Piston construction



Nov. 6, 1951 v. c. STERRETT 2,574,299

PISTON CONSTRUCTION Original Filed Deo. 51, 1947 ATTORNEYS Patented Nov. 6, 1951 PISION CONSTRUCTION Vance C. Sterrett, Lcgansport, Ind.

Original application December 31, 1947, Serial No.

794,975, now Patent No. 2,493,602, dated January 3, 1950. Divided and this application August 5, 1949, Serial No. 108,779

9 Claims.

My present invention relates to fiuid motor pistons and is a division of my copending application Serial No. '794,975 led December 31, 1947, now Patent 2,493,602 granted January 3, V1950.

An object of my invention is the provision of a novel means of constructing a piston and rod assembly wherein the elements interlock in such a manner as to obviate the use of screw threads or other conventional connecting means.

Another object of the invention is to provide a piston comprising complementary face discs which are locked in position on the piston rod by concentric shear and wear rings.

A further object of my invention is the provision of a pair of juxtaposed face discs having peripheral recesses for accommodation of selfadjusting packing rings which cooperate with the inner wall of the fluid motor cylinder.

A still further object of this invention is to provide a piston construction which is economical to manufacture and maintain and which may be quickly and easily assembled or disassembled relative to its associated cylinder.

To these and other ends my invention comprises further improvements and advantages as willbe further described in the accompanying specification, the novel features thereof being set forth in the appended claims.

In the drawings:

Figure 1 is a central longitudinal cross section of a power force cylinder embodying my invention.

Figure 2 is a vertical cross section taken on the line 2-2 illustrating the construction and arrangement of the locking rings which secure the piston sections to its shaft and to each other.

Similar reference numerals, in the several gures, indicate similar parts.

In carrying out my invention the uid power unit comprises a hydraulic cylinder I of an internal diameter suitable to the ultimate power to be delivered and of a length selected according to the nature of the work to be performed by the enclosed piston and piston rod. The ends of the cylinder are closed by the opposed heads I I and I2 having inner or proximate ends I3 and I4 which t closely Within the ends of the cylindex', their remaining outer portions being of such dimensions as to accommodate i'luid inlet or outlet ports I5 and I 6 and take piston rod packing glands I 'I and I8 located outwardly beyond said ports. As is common practice in the operation of hydraulic cylinders the source of fluid pressure be it oil, water or air is connected through a four way control valve to the ports I5 and I6 so that it may alternately be introduced at the one end of the cylinder to act on one side of the piston and allowed to exhaust from the opposite side of the piston. Since this master valve is well known in the art I have omitted illustration thereof.

A detail to be mentioned in regard to the packing glands I'I-I8 is that snap rings 'IS-'I9 are provided both in front and rear of said glands. Outside of the latter the end portions of the shaft are carried by'and journaled in journal rings --8I which back up the packings and are themselves held in place by snap rings 82, all of said rings being held in place by the engagement of their outer points in annular recesses formed En the walls of the recesses III and H2.

The union between the heads and the cylinder is effected by providing the respective overlapping parts with mating annular recesses, of suitable depths which accommodate a locking strip 2I. The latter is preferably rectangular in cross section and capable of withstanding a shear strain in excess of any internal pressure that may be applied to a given cylinder. To facilitate the application of the locking strip 2I there is provided an opening in the the wall of the cylinder leading from its recess and at a point in the bottom of the recess in the head there is a drilled hole for the reception of a pin. The outer end of the latter is approximately equal to the depth of recess in the head and extending across the inner end of the locking strip is a recess by means of which the strip is hooked in engagement with the pin when its forward end is inserted in the opening in the wall of the cylinder. From this arrangement of parts it will be seen that by effecting a relative rotation of the cylinder and a cylinder head the locking strip will be drawn inwardly to effect a complete encirclement of the head to securely unite it to the end of the cylinder without the use of any other means of attaching the parts.

In the inner ends I3--I4 of the two heads I provide annular channels and insert therein rubber rings IIa and I 2a. The cross sectional diameter of these is such that they are normally compressed against the cylinder wall when the heads are inserted.

The piston rod 3| extends through the heads II and I2 axially of the cylinder I0 and centrally mounted thereon is the piston the construction of which and the means for holding it rigidly connected to the rod comprises an important part of my invention. As shown in Fig. 1 the piston comprises two similar right and left hand disc shaped parts 32, 33 bored centrally to receive the rod and of a diameter somewhat less than that of the cylinder. On the shaft between the meeting faces of the two discs forming the piston is an annular groove and fitted therein are two semi-circular sections 34, 35 (Fig. 2) which form a shear ring 36 (Fig. 1). One half of the thickness of the ring extends beyond the face of the rod 3| and is received in and held in place on the shaft by recesses formed in the adjacent faces of the piston discs, which are also formed to accommodate packing rings 36El which are triangular in cross section. It should be noted that the arrangement or the shape of .the packing rings 36a is by no means critical since their sole purpose is to prevent fluid from passing from one side of the piston to the other and between the piston discs and piston rod 3,1. Any. conventional seal ring .placed between the opposing surfaces of the discs and piston rod would suflice and could be retainedV in a groove formed in either the discs or the piston rod. The type of rings shown merely as an illustration at 36a could be retained in a number of ways including conventional methods of bonding. In lateral depth the last-mentioned recesses are slightly less than one half the width of the shear ring 3 for the purpose of `holding the faces of the disc apart sufficiently and provide a space 31 -to allow for inaccuracies of machining,

The peripheries ofthe piston discs are each recessed to provide them with annular flanges 32a, 33a on their adjacent edges and similar flanges 32h, 33b on their outer edges. Surrounding the piston Yand snugly fittingthe space between it and the cylinder wall with a sliding t therein is a wear ring..40 (Fig. l) composed of two parts 4I, 42 (Fig. 2) lwhich are recessed on their inner faces to provide lateral shoulders 48a, 40b which straddle the central piston flanges 32a, 33a. Also l carried on the circumference of the piston discs are piston packing rings 43, 44. These may be cup shaped in cross section as shown for the purpose of illustration. They face in opposite .directions and are .backed against shims'431-llla lying at .the opposite sides `of the central wear ring 40 and held in this position by the outer flanges 32h, 33". on the piston discs. These shims serve to close the spaces-.between the meeting ends of the semi-circular portions of the ring 43 to prevent the composition packing ring from being extended thereinto. They are cut'circularly to sizek from thin metal and to permit their application in place are severed at one .place on a diagonal line.

From the foregoing description of'my .present invention it will be Vseen that I .have devised a vnovel piston construction wherein .the simplicity and efficiency of its yinterlocking elements produce a decided-advantage and-advancement in the Yhydraulic media art. This construction has provided the vindustry with a `new tpistonv which is not onlyA more eiiicient iniits functioncin connection with a fluid motor,butwhich is also economical as to original manufacture and as to time and labor subsequently required for assembly and'disassembly of the unit.

While a preferred form of the `invention has -been Vshown anddescribed, it will-beunderstood that variation 'in details -of form may be made 'f without departure from the inventionas defined Ain the appendedv claims.

Iv claim: J1. In a fluid motor comprising a cylinder and heads thereon, a'piston'rod guided .in the'heads having an intermediate annular recess, a ring fitted in the rod recess and extending beyond its periphery, piston discs on the rod at opposite sides of said ring, a second ring overlapping the proximate faces of the discs serving to hold them in engagement with said first ring and piston packings carried on the peripheries of said discs at each side of said second ring.

2. In a fluid motor comprising a cylinder and vheads thereon, a piston rod guided in the heads having an intermediate annular recess, a shear ring fitted in the rod recess and extending beyond itsV periphery, piston discs on the rod at opposite sides of said ring, a wear ring overlapping the proximatev faces of the discs serving them in engagement with saidl shear ring and packing rings ,carried on the peripheries of said discs at each side of the wear ring.

3. In a fluid motor comprising a cylinder and heads thereon, a piston rod guided in the heads having an intermediate annular recess, piston discs on the rod having in their proximate faces cavities alined with said recess, means fitted in the rod recess and extending beyond its periphery for reception by said cavities, flanges on the peripheries of the discs, a ring surrounding said discs and embracingv said flanges to lock the discs together and packing rings on the discs at opposite sides ofi-said ring.

4. In a fluid motorcomprising a cylinder and heads thereon, a piston rod guided in the heads having an intermediate annular recess, 4va shear ring rectangular. in crosssection tted -in the. rod recess and'extendingbeyond its periphery, piston discs on the rod having in'their proximate faces cavities receiving approximately one half of ythe ring, flanges on the peripheriesof the discs, a wear ring surrounding said discs and embracing said flanges to lock the discs together and piston packings on the discsat opposite sides of the wear ring.

5. In a fluid motor .comprising a'cylinder land heads thereon, a piston rod guided in the heads having an intermediateannular recess, a-divided shear ring -tted in the rod recess and extending beyond litsperiphery, piston discs on therodhaving in their proximate faces cavities receiving approximately one.v half-of .the ring,l angeson the peripheries of the discs at their vproximate faces, a sectional wear ring surrounding-said discs and embracing said flanges to lock the discs together and-piston packingsonthe discs at opposite sides of the wear ring.

6. In a fluid motor comprising a cylinder and heads thereon, a piston-rod-guided in the heads having an intermediate annular recess, a two part shear ring fitted in the recess forming an abutment-on the rod, circular piston discs on vthe rod engaging opposite sides of. said 'abutmenta outwardly extending pairs; of spaced flangCS 0n `the periphery of the'discs 'forming annular lgrooves therein, a two part wear ringvgrooved on its inner face embracing theproximate flanges on the two discs and serving to -lock them yin engagement with the shear ring-and pistonrings lying in the piston Vdisc grooves at lopposite sides of .the Wear ring.

' 7. Ina fluid vmotor-comprising a cylinder and heads thereon, a-piston rod guided in the heads having an intermediate annular recess, a rtwo part shear ring fitted inthe recess'forming anabutment on the yrodycircular piston discs on the rod engaging oppositesides of said abutmentsfoutwardly extending pairs of spaced flanges on the periphery of -the discs- -formingfannular grooves therein,vr a two-part 'wearring groovedon its .-in-

ner face embracing the proximate anges on the two discs and serving to lock them in engagement with the shear ring and piston rings lying in the piston disc grooves at opposite sides of the wear ring, and shims between each of said piston rings and said Wear ring.

8. In a fluid motor comprising a cylinder and heads thereon, a piston rod guided in the heads having an intermediate annular recess, a shear ring rectangular in cross section tted in the rod recess and extending beyond its periphery, piston discs on the rod having in their proximate faces cavities receiving approximately one half of the ring, a packing ring between each disc and the piston rod, flanges on the peripheries of the discs, a Wear ring surrounding said discs and embracing said flanges to lock the discs together and piston packings on the discs at opposite sides of the wear ring.

9. In a fluid motor comprising a cylinder and heads thereon, a piston rod positioned coaxial with and slidable relative to at least one of said heads, a piston assembly attached to said piston rod and slidable relative to the inner surface of said cylinder, said piston rod having an intermediate annular recess, arcuate segments tted therein and radially extending beyond the periphery of Cil the piston rod, piston discs fitted to the piston rod at both sides of the radially extending arcuate segments and provided with proximate face cavities enveloping the extended portion of said segments, said piston discs having annular oustanding flanges on their proximate peripheral edges, a segmented wear ring circumventing the piston discs and having annular inwardly extending flanges at both Sides suitably spaced to embrace the flanges on the piston discs, piston cup rings positioned to each side 0f said Wear ring with their backs toward said wear ring and retained by outwardly extending annular flanges formed out of the remote peripheral edges of the piston discs and shims interposed between said cups and wear ring.

VANCE C. STERREFII.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 531,723 Hill Jan. 1, 1895 648,079 Prince, Jr Apr. 24, 1900 2,059,446 Eastman Nov. 3, 1936 

